The present invention relates to pressure-sensitive adhesive constructions used for making tags, labels and the like and, more particularly, to pressure-sensitive adhesive constructions comprising a thin continuous film disposed onto a layer of a pressure-sensitive adhesive that renders an underlying pressure-sensitive adhesive layer surface tack free, and that is printable, convertible and dispensable.
Pressure-sensitive adhesive (PSA) constructions such as labels, tapes, decals and the like are known in the art. For example, PSA label constructions are commonly used to apply a particular face stock having a specific nature of printing to an object or article, and are especially useful where objects having low surface energies are to be labeled. PSA label constructions typically comprise a liner, a PSA layer disposed onto the liner and a face stock laminated onto the PSA layer. The face stock is typically made from a web or sheet of paper, cardboard or plastic and is applied or laminated to the PSA layer sequentially at some time after the application of the PSA layer. The face stock is printed on with information or other indicia before or after it is laminated onto the PSA layer. The conventional PSA label construction is applied to an article surface or other substrate surface by removing the liner to expose the PSA layer and placing the PSA layer into contact with the desired surface, wherein the face stock remains attached to the opposite surface of the PSA layer.
In the manufacture and production of PSA constructions, a substantial amount of the overall cost involved is in the material costs for the face stock. be it paper, cardboard, or plastic. Additionally, where the tag or label is to be adhered to a contoured or irregular surface, and where a high degree of flexibility is desired. the rigidity of the face stock may interfere with the application and the adherence of the tag or label. Further, conventional PSA label constructions require sequential processing of the PSA layer and face stock, thereby lengthening the amount of time needed to manufacture a completed PSA label construction.
It is, therefore, desired that a PSA construction be constructed for use as a label, tag, tape, decal and the like that avoids the need to use a conventional face stock formed from paper, cardboard or plastic. It is desired that the PSA label construction have printability, convertibility and dispensability properties that are better than or equal to that of PSA label constructions having a conventional face stock. It is also desired that such PSA label construction be designed in a manner that reduces the amount of manufacturing time needed to complete the same, when compared to a PSA construction comprising a conventional face stock.
Faceless PSA label constructions of this invention are constructed without having a conventional face stock for printing indicia thereon but, rather comprise a thin, printable, convertible and dispensable continuous film disposed on an underlying PSA layer, that is preferentially removed with the PSA from a release liner to facilitate application onto a designated substrate. In an example embodiment, faceless PSA label constructions of this invention comprise a flexible substrate having a release surface, and a layer of pressure-sensitive material disposed on the release surface, and a continuous film is disposed over a surface of the layer of pressure-sensitive adhesive to render the pressure-sensitive adhesive tack free. The final film-forming layer is derived from a coatable or extrudable fluid with film-forming properties that is delivered to the pressure-sensitive adhesive layer in either 100 percent solids form, in an emulsion latex, or dissolved in a suitable solvent. Upon cooling or with removal of the water or solvent, a continuous, printable, self supporting film with measurable tensile, elongation, and tear properties is formed.
The continuous film is selected from the group of film-forming polymers consisting of polyamide resins, polyester resins, polyurethane resins, polyacrylate resins, vinyl acetate resins, and mixtures thereof. Because it is desired that the continuous film be self supporting, the continuous film has a tensile strength of at least 200 psi, and a percent ultimate elongation of at least 50. The continuous film can be applied sequentially or simultaneously with the pressure-sensitive adhesive. For purposes of simultaneous application it is desired that the continuous film be formed from a material having a hot melt viscosity that is within a factor to two times that of a hot melt viscosity for the PSA. The completed faceless PSA construction thus formed is capable of receiving and retaining printing and marking indicia directly onto the surface of the continuous film.
Faceless PSA constructions of this invention can be used as a label, tag, tape, decal and the like that avoids the need to use a conventional face stock formed from paper, cardboard or plastic. thereby eliminating application limitations regarding the same, e.g., now permitting application of label onto substrates having irregular surfaces. PSA constructions of this invention are self supporting and display printability, convertibility and dispensability properties that are better than or equal to that of PSA label constructions having a conventional face stock. PSA constructions of this invention also reduce manufacturing costs, avoiding the need to use a separate paper, cardboard, metallic or plastic face stock, and increase manufacturing efficiency by permitting simultaneous application of the continuous film layer and PSA, when compared to a PSA construction comprising a conventional face stock.